Respuesta :
Answer:
Density change, Δρ = 2.4 × 10⁻⁴ kg/m³
Temperature Change, ΔT = 0.0258 K
Velocity Change, Δc = 0.0148 m/s
Explanation:
For sound waves moving through the air,
Pressure and Temperature varies thus
(P₀/P) = (T₀/T)^(k/(k-1))
Where P₀ = initial pressure of air = 101KPa = 101000 Pa
P = final pressure of air due to the change brought about by the moving sound wave = 101000+30 = 101030 Pa
T₀ = initial temperature of air = 30°C = 303.15 K
T = final temperature of air = ?
k = ratio of specific heats = Cp/Cv = 1.4
(101000/101030) = (303.15/T)^(1.4/(1.4-1))
0.9990703 =(303.15/T)^(3.5)
Solving This,
T = 303.1758 K
ΔT = T - T₀ = 303.1758 - 303.15 = 0.0258 K
Density can be calculate in two ways,
First method
Δρ = ρ - ρ₀
P₀ = ρ₀RT₀
ρ₀ = P₀/RT₀
R = gas constant for air = 287 J/kg.k
where all of these are values for air before the wave propagates
P₀ = 101000 Pa, R = 287 J/kg.K, T₀ = 303.15K
ρ₀ = 101000/(287 × 303.15) = 1.1608655 kg/m³
ρ = P/RT
P = 101030 Pa, T = 303.1758K
ρ = 101030/(287×303.1758) = 1.1611115 kg/m³
Δρ = ρ - ρ₀ = 1.1611115 - 1.1608655 = 0.00024 kg/m³ = 2.4 × 10⁻⁴ kg/m³
Second method
(ρ₀/ρ) = (T₀/T)^(1/(k-1))
Where ρ₀ is initially calculated from ρ₀ = P₀/RT₀, then ρ is then computed and the diff taken.
Velocity Change
c₀ = √(kRT₀) = √(1.4 × 287 × 303.15) = 349.00669 m/s
c = √(kRT) = √(1.4 × 287 × 303.1758) = 349.0215415 m/s
Δc = c₀ - c = 349.0215415 - 349.00669 = 0.0148 m/s
QED!
In this exercise we have to use the pressure knowledge to calculate the velocity, temperature and density so we have:
- Density: [tex]\Delta \rho = 2.4 * 10^{-4} kg/m^3[/tex]
- Temperature: [tex]\Delta T = 0.0258 K[/tex]
- Velocity: Δc = 0.0148 m/s
The variation of temperature and pressure is given by the formula of:
[tex](P_0/P) = (T_0/T)^{(k/(k-1))}[/tex]
From the formula given above we can identify:
- P₀ = initial pressure of air
- P = final pressure of air due to the change brought about by the moving sound wave
- T₀ = initial temperature of air
- T = final temperature of air
- k = ratio of specific heats
Solving the formula for temperature we find:
[tex](101000/101030) = (303.15/T)^{(1.4/(1.4-1))}\\0.9990703 =(303.15/T)^{(3.5)}\\T = 303.1758 K\\\Delta T = T - T_0 = 303.1758 - 303.15 = 0.0258 K[/tex]
They are using the formula for density is:
[tex]\rho_0 = 101000/(287 * 303.15) = 1.1608655 kg/m^3\\\rho = P/RT\\\rho = 101030/(287*303.1758) = 1.1611115 kg/m^3\\\Delta \rho = 2.4 * 10^{-4} kg/m^3[/tex]
Calculating the speed we find that:
[tex]c_0 = \sqrt{kRT_0} = 349.00669 m/s\\c = \sqrt{kRT} = 349.0215415 m/s\\\Delta c = 0.0148 m/s[/tex]
See more about presure at brainly.com/question/356585
